The coming few years will bring a halt to the dominance of big pharmaceutical companies, which are exposed to patents that will expire on more than $80 billion-worth of blockbuster drugs. A famous example is the patent expiry of Eli Lilly's anti-depressant drug, Prozac, which reportedly lost 73% of market share within two weeks of generic launch. Similarly, Pfizer's anti-depressant Zoloft, which lost patent exclusivity, showed a decline in revenues to $531 million in 2007, compared to $3.3 billion in 2005. However, Pfizer's bigger concern in the near future is when the patent for other famous drugs such as Lipitor and Viagra will expire.